Terrence Mitchell Riley (born June 24, 1935), is an American composer and performing musician best known as a pioneer of the minimalist school of composition. Influenced by jazz and Indian classical music, his music became notable for its innovative use of repetition, tape musictechniques, and delay systems. His best known works are the 1964 composition In C and the 1969 LP A Rainbow in Curved Air, both considered landmarks of minimalism and important influences on experimental, rock, and contemporary electronic music.

Raised in California, Riley began studying composition and performing solo piano in the 1950s. He befriended and collaborated with composer La Monte Young, and later became involved with the San Francisco Tape Music Center. A two-record deal with CBS in the late 1960s, resulting in an LP recording of In C (1968) and A Rainbow in Curved Air (1969), brought his work to wider audiences. In the 1970s, he began intensive studies under Hindustani singer Pandit Pran Nath, whom he often accompanied in performance. He has collaborated frequently throughout his career, most extensively with chamber ensemble the Kronos Quartet and his son, guitarist Gyan Riley.

Born in Colfax, California, in 1935, Riley began performing as a solo pianist during the 1950s. During that decade, he studied composition at San Francisco State University, the San Francisco Conservatory, and University of California, Berkeley, studying with Seymour Shifrin and Robert Erickson. He befriended composer La Monte Young, whose earliest minimalist compositions using sustained tones were an influence; together, Young and Riley performed Riley’s improvisatory composition Concert for Two Pianists and Tape Recorders in 1959–60.